fix: improve SQLite concurrency and database logging reliability

Database improvements:
- Enable WAL mode for better concurrent read/write access
- Add busy_timeout (30s) to wait for locked database
- Add synchronous=NORMAL for balanced safety/performance
- Configure check_same_thread=False for thread safety

Logging improvements:
- Add retry logic (3 attempts) for database locked errors
- Silently skip logging on persistent failures to avoid spam
- Properly rollback failed transactions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/core/database.py

@@ -10,12 +10,39 @@ This module provides classes and functions for:
 
 import logging
 
-from sqlalchemy import create_engine
+from sqlalchemy import create_engine, event
 from sqlalchemy.orm import declarative_base, sessionmaker
 
 from .config import settings
 
-engine = create_engine(settings.database_url)
+
+def _configure_sqlite_connection(dbapi_connection, connection_record):
+    """Configure SQLite connection for better concurrency.
+
+    - WAL mode: Allows concurrent reads during writes
+    - busy_timeout: Wait up to 30 seconds if database is locked
+    - synchronous=NORMAL: Balance between safety and performance
+    """
+    cursor = dbapi_connection.cursor()
+    cursor.execute("PRAGMA journal_mode=WAL")
+    cursor.execute("PRAGMA busy_timeout=30000")
+    cursor.execute("PRAGMA synchronous=NORMAL")
+    cursor.close()
+
+
+# Create engine with SQLite-specific configuration
+engine_kwargs = {}
+
+# Add SQLite-specific settings for better concurrent access
+if settings.database_url.startswith("sqlite"):
+    engine_kwargs["connect_args"] = {"check_same_thread": False}
+
+engine = create_engine(settings.database_url, **engine_kwargs)
+
+# Configure SQLite pragmas on connection
+if settings.database_url.startswith("sqlite"):
+    event.listen(engine, "connect", _configure_sqlite_connection)
+
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
 Base = declarative_base()